The present invention relates to self-excited alternators of the brushless type, having a rotating field which is excited by an alternating current exciter whose rotating armature is mounted to rotate with, and is permanently connected to the field winding of the alternator via field rectifier means also mounted to rotate with the field winding. The exciter has one or more exciter stator primary windings and one or more rotary exciter secondary windings connected via rotary field rectifier means to the rotary main field winding of the alternator. Primary excitation direct current for the exciter is derived, via magnetic coupling, from a rotary auxiliary magnetic field produced by a feedback winding connected in series with the main field winding and mounted to rotate therewith.
Australian Patent Application No. 37930/85 describes such a construction wherein the primary excitation current is derived by rectification of the current induced into an auxiliary stator secondary winding located within the auxiliary magnetic field. The magnetic circuit coupling the rotary feedback winding with the auxiliary stator secondary winding is common with that of the exciter.
With such a construction, efficient exciter primary to exciter secondary power transfer is important as well as efficient transfer of power between the feedback winding or windings and auxiliary stator secondary winding or windings.
Effective operation of such a self-excited alternator may be adversely affected by undesired voltages induced into the exciter primary winding by the magnetic field of the feedback winding, into the feedback winding by the magnetic field of the exciter primary winding, into the exciter secondary winding by the influence of the magnetic field of the feedback winding upon the magnetic field of the exciter primary winding, and/or into the feedback secondary winding by the influence of the magnetic field of the exciter primary winding upon the magnetic field of the feedback winding.